Through his brother-in-law Sir
Henry Sidney he was connected with the Dudleys, and it was the Earl of Leicester
who knighted him in 1565. Like them he was
inclined to puritanism, being described as ‘an earnest furtherer of
religion’ by the Bishop of Lincoln in 1564. During
Parliament of 1572 he was named to committees on a private bill for Lord Stourton (13
Mar 1576) and the Queen's safety (25 Jan 1581).

Near the end of his life Harrington was
noted by Lord Burghley as a ‘knight of great possessions’, fit to be made a
baron. His will, dated 7 Apr 1591, made generous provision for his servants and
friends. Nearly all his lands went to his
eldest son, John, who received a barony in 1603. One manor, certain leases and
tenements were divided between his younger sons Henry and James, whom he made
joint executors. Subsequently, by a codicil dated 22 Jan 1592, just before his death,
he appointed James sole executor and it was he who proved the will
four days later, afterwards erecting at Exton a fine monument to his parents.

Some sources gives his age at death as
80 but the other make him several years younger.